This application claims the priority of German application 197 43 597.1, filed Oct. 2, 1997 in Germany, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an open-end spinning rotor comprising a fiber sliding surface and a fiber collecting groove containing plated surfaces, in which hard particles of a certain size are embedded.
It is disclosed in German published patent application 43 05 626 that the fiber collecting groove relative to the fibers to be spun has a greater frictional resistance than the fiber sliding surface. This permits the fibers to slide sufficiently rapidly to the fiber collecting groove and thereafter, at the latest at the point of the fiber collecting groove, to take on the speed of the spinning rotor. All the surfaces of the spinning rotor are provided with a nickel-diamond plating, whereby the desired roughness in the fiber collecting groove is achieved in that individual diamond particles of a certain size project out from the plating. The fiber sliding surface in contrast is subsequently smoothed, such that a large proportion of the diamond grains are pulled out, whereby the fiber sliding surface loses its undesirable strong grip effect.
The disadvantage is that the fiber sliding surface is not sufficiently wear resistant anymore after the diamond particles have been pulled out.
It is an object of the present invention to plate an open-end spinning rotor of the above mentioned type in such a way that the fiber sliding surface as well as the fiber collecting groove are sufficiently protected against wear, and that the fiber collecting groove has a better grip effect relative to the fibers to be spun than the fiber sliding surface.
This object has been achieved in accordance with the present invention in that the plating is so configured that the particles embedded in the fiber collecting groove are larger than those embedded in the fiber sliding surface after a certain length of operation spinning time.
By means of the hard particles provided in the fiber collecting groove as well as the fiber sliding surface, a sufficiently high wear resistance of the open-end spinning rotor is achieved. Because the particles belonging to the fiber collecting groove are larger than the particles belonging to the fiber sliding surface, the fiber collecting groove has the greater grip effect relative to the fibers to be spun in comparison to the fiber sliding surface.
In an embodiment of the present invention it is provided that the plated surfaces originally comprise a first plating containing particles of a larger size and a second plating on top of the first containing particles of a smaller size.
The latter applied plating containing the smaller sized particles is sufficiently smooth and is suitable for a fiber sliding surface, and is also sufficiently wear resistant, at least on the fiber sliding surface. The fibers can thus slide on the fiber sliding surface into the fiber collecting groove, without an undesirable friction wear occurring on the fiber sliding surface. Using the correct choice of particle size, the grip effect of the fiber collecting groove is at first sufficient; however, the wear is greater in this area of the open-end spinning rotor. The reason for this is that the fibers fed into the fiber collecting groove--in contrast to the fiber sliding surface--receive an additional twist, as the yarn twist lasts right into the fiber collecting groove. This results in a faster friction wear of the latterly applied plating in the fiber collecting groove. Thus after only a few hours operation, the underlying plating containing the larger hard particles is exposed. The larger-sized particles ensure, however, that the wear on the fiber collecting groove is significantly slowed down. At the same time, the trip effect of the fiber collecting groove increases, so that the yarn quality does not worsen overall. After a certain operation time, a fiber collecting groove with more grip effect than the fiber sliding surface is relatively quickly achieved, as the upper plating containing the smaller particles is worn off and the underlying plating containing the larger particles is exposed. Thus after a short running-in time of the open-end spinning rotor, the ideal situation is reached whereby the fiber sliding surface as well as the fiber collecting groove is sufficiently wear resistant, the fiber collecting groove nevertheless having, in relation to the fibers to be spun, the stronger grip effect in comparison to the fiber sliding surface.
Practical experience has shown that it is favorable when the first as well as the second plating are each a nickel-diamond plating. Nickel-diamond plates create excellent spinning conditions and can be adapted, with regard to the particle size, to the desired requirements.
It has proven to be advantageous when the larger particle size measures circa between 2.5 and 4 .mu.m (mean diameter of the particle grain size), and the smaller particle size measures circa 1.5 to 2 .mu.m. This is a good compromise as regards yarn quality and wear protection.
In order that, on the one hand the open-end spinning rotor achieves adequate endurance, and on the other that the upper plating in the fiber collecting groove is worn down as quickly as possible, the first plating should have a thickness of approximately 20 to 30 .mu.m and the second plating a thickness of approximately 10 to 15 .mu.m.
It is also advantageous when the percentage of particles in the first plating is higher than the percentage of particles in the second plating. Thus the different grip effect in the fiber collecting groove and in the fiber sliding surface is achieved not only by means of the different-sized particles, but also by means of the different percentages of particles in the plates.